Electromagnetic clutches typically are used to transmit power from a lawn mower engine to two or more cutting blades mounted on spindles under a mower deck. The electromagnetic clutches are designed to engage very quickly to minimize clutch plate wear. However, a disadvantage of the sudden engagement is that engine speed may droop. As a result, the mower deck may vibrate and shake until the rotational speed of the blades and spindles increases sufficiently.
Soft engagement electronic control systems or modules have been proposed that are intended to reduce the suddenness of the clutch engagement, by modulating the voltage applied to the electromagnetic coils. The soft engagement should allow the clutch plates to slip for a longer period while reducing engine droop and other undesirable characteristics of a hard start.
For example, U.S. Pat. No. 5,094,332 relates to a soft start controller for regulating the engagement and disengagement of an electromagnetic clutch. A microprocessor may be programmed to regulate the current controller such that the electrical current which is supplied to the clutch during the engagement process follows a selected one of three clutch energizing current curves, or any other curve which may be programmed into the memory circuit. The microprocessor is programmed to select one of the curves before the engagement sequence begins in response to the status of one or more parameters sensed by sensors such as a speed sensor, temperature sensor, engine vacuum sensor and level sensor.
However, conditions may change once the operator actuates the clutch engagement control and as the clutch moves into engagement. For example, the amount of grass and debris buildup under the mower deck may change, and there may be swings in engine power, during the engagement process. Additionally, clutch face wear and belt wear may change the engagement dynamics. As a result, a clutch energizing curve selected at initiation of engagement may no longer be desirable or optimal. None of the programmed clutch energizing curves may be optimal for a particular engine and mower deck, especially after they are subject to wear from use. Further, the programmed set of clutch energizing curves may not be suitable for all combinations of mower deck widths and engines. A soft start system that may be optimal for one mower under one set of conditions may not produce the same desired outcome under different conditions, on a different model, or on a mower with a different mower deck and engine configuration.
A soft start system for clutch engagement is needed that adapts if conditions change while the clutch moves into engagement. A soft start system for clutch engagement is needed that can adapt to provide an optimal clutch energizing curve for a particular mower deck and engine after they are subject to wear from use or other factors that could affect the engagement dynamics. A soft start system for clutch engagement is needed that can adapt so that it is suitable for many different combinations of mower deck widths and engine configurations. A soft start system is needed that may be adapted to mowers under any set of conditions, and for mowers having various different mower deck and engine configurations.